1. Field of the Invention
The present invention relates to a heat exchanger provided with a casing, received in which casing is a heat exchanger core provided with a pair of inlet/outlet convex portions in its opposite end portions, wherein the core has its inlet/outlet convex portions project outward from the casing, and a difference in thermal expansion between the casing and the core is adequately absorbed in the heat exchanger.
2. Description of the Related Art
A conventional heat exchanger is provided with a casing, which receives therein a heat exchanger core. A pair of inlet/outlet convex portions, for example such as inlet/outlet pipes and their corresponding boss portions in which the inlet/outlet pipes are mounted, are provided in opposite longitudinal end portions of the core. The inlet/outlet convex portions or pipes pass through the casing through a pair of through-hole portions of the casing, are brought into fluid-tight contact therewith and fixedly mounted therein through a suitable fixing means such as soldering and the like. A first fluid is introduced into the core through these inlet/outlet pipes. On the other hand, a second fluid is introduced into the casing so that the exchange of heat between the first and the second fluid is conducted in the conventional heat exchanger.
Now, the problem to be solved by the present invention will be described.
In the conventional heat exchanger having the above construction, for example, cold water which serves as the second fluid is introduced into the casing. On the other hand, hot fluid serving as the first fluid is introduced into the core. Under such circumstances, the casing reaches substantially the same temperature as that of the cold water. On the other hand, the core reaches substantially the same temperature as that of the hot fluid. In this case, the core is larger in thermal expansion than the casing, which causes thermal stresses to concentrate in root portions of the inlet/outlet pipes. Consequently, due to such concentration of the thermal stresses, there is a fear that a crack is produced in the root portions of the inlet/outlet pipes in use.